Baculovirus-mediated promoter assay and transcriptional analysis of white spot syndrome virus orf427 gene

Background White spot syndrome virus (WSSV) is an important pathogen of the penaeid shrimp with high mortalities. In previous reports, Orf427 of WSSV is characterized as one of the three major latency-associated genes of WSSV. Here, we were interested to analyze the promoter of orf427 and its expression during viral pathogenesis. Results in situ hybridization revealed that orf427 was transcribed in all the infected tissues during viral lytic infection and the translational product can be detected from the infected shrimp. A time-course RT-PCR analysis indicated that transcriptional products of orf427 could only be detected after 6 h post virus inoculation. Furthermore, a baculovirus-mediated promoter analysis indicated that the promoter of orf427 failed to express the EGFP reporter gene in both insect SF9 cells and primary shrimp cells. Conclusion Our data suggested that latency-related orf427 might not play an important role in activating virus replication from latent phase due to its late transcription during the lytic infection.